Merge pull request ssrg-vt#2 from tv-deusen/dup2

dup2 implementation

arch/x86/kernel/isrs.c

@@ -442,6 +442,14 @@ void syscall_handler(struct state *s)
 			break;
 #endif /* DISABLE_SYS_MADVISE */
 
+#ifndef DISABLE_SYS_DUP2
+		case 33:
+			/* dup2 */
+			s->rax = sys_dup2(s->rdi, s->rsi);
+			break;
+#endif /* DISABLE_SYS_DUP2 */
+
+
 #ifndef DISABLE_SYS_NANOSLEEP
 		case 35:
 			/* nanosleep */

include/hermit/minifs.h

@@ -18,5 +18,12 @@ int minifs_write(int fd, const void *buf, size_t count);
 uint64_t minifs_lseek(int fd, uint64_t offset, int whence);
 int minifs_mkdir(const char *pathname, mode_t mode);
 int minifs_rmdir(const char *pathname);
+/**
+ * MiniFS implementation of dup2.
+ * Attempts to follow Linux convention of
+ * error handling with regards to 
+ * bad file descriptors.
+*/
+int minifs_dup2(int oldfd, int newfd);
 
 #endif /* MINI_FS_H */

include/hermit/stddef.h

@@ -95,6 +95,7 @@ extern uint64_t tux_start_address;
 #define UHYVE_PORT_FDATASYNC	0x527
 #define UHYVE_PORT_SYNCFS		0x528
 #define UHYVE_PORT_GETDENTS		0x529
+#define UHYVE_PORT_DUP2         0x530
 
 // Networkports
 #define UHYVE_PORT_NETINFO             0x505

include/hermit/syscall.h

@@ -207,6 +207,7 @@ int sys_syncfs(int fd);
 long sys_set_tid_address(int *tidptr);
 int sys_getdents(unsigned int fd, struct linux_dirent *dirp,
 		unsigned int count);
+int sys_dup2(int oldfd, int newfd);
 
 struct ucontext;
 typedef struct ucontext ucontext_t;

kernel/minifs.c

@@ -23,6 +23,8 @@
 #define SEEK_CUR		1
 #define SEEK_END		2
 
+#define IS_OPEN(fd) (fds && (fds[fd].f != NULL))
+
 typedef struct s_file {
 	char *name;
 	uint64_t size;
@@ -262,6 +264,23 @@ int meminfo_read(int fd, void *buf, uint64_t len) {
 	return len;
 }
 
+int minifs_dup2(int oldfd, int newfd) {
+
+	if (!IS_OPEN(oldfd) || newfd > MAX_FDS) {
+		return -EBADF;
+	}
+
+	if (IS_OPEN(newfd) && !minifs_close(newfd)) {
+		LOG_ERROR("minifs_dup2: failed to close open file with fd: %d\n",
+			newfd);
+		return -1;
+	}
+
+	fds[newfd].f = fds[oldfd].f;
+	fds[newfd].offset = fds[oldfd].offset;
+
+	return 0;
+}
 
 int meminfo_write(int fd, const void *buf, uint64_t len) {
 	return len;

kernel/syscalls/dup2.c

@@ -0,0 +1,41 @@
+#include <hermit/syscall.h>
+#include <hermit/logging.h>
+#include <hermit/errno.h>
+#include <asm/uhyve.h>
+#include <asm/page.h>
+#include <hermit/minifs.h>
+
+extern int hermit_dup2(int oldfd, int newfd);
+
+typedef struct {
+    int oldfd;
+    int newfd;
+    int ret;
+} __attribute__ ((packed)) uhyve_dup2_t;
+
+
+int sys_dup2(int oldfd, int newfd)
+{
+    if (unlikely(newfd == oldfd))
+        return newfd;
+
+#ifndef NO_NET
+    if ((oldfd & LWIP_FD_BIT) || (newfd & LWIP_FD_BIT)) {
+        LOG_ERROR("dup2: sockets not supported\n");
+        return -ENOSYS;
+    }
+#endif
+
+    if (likely(is_uhyve())) {
+
+        if (minifs_enabled)
+            return minifs_dup2(oldfd, newfd);
+
+        uhyve_dup2_t uhyve_args = {oldfd, newfd, -1};
+        uhyve_send(UHYVE_PORT_DUP2, (unsigned)virt_to_phys((size_t)&uhyve_args));
+        return uhyve_args.ret;
+    }
+
+    LOG_ERROR("dup2: not supported with qemu isle\n");
+    return -ENOSYS;
+}

kernel/syscalls/fcntl.c

@@ -48,6 +48,8 @@ int sys_fcntl(int fd, unsigned int cmd, unsigned long arg) {
 		}
 
 		switch(cmd) {
+			case F_GETFL:
+			case F_GETFD:
 			case F_SETFD:
 				u_arg.fd = fd;
 				u_arg.cmd = cmd;

tools/uhyve-syscalls.h

@@ -49,7 +49,8 @@ typedef enum {
 	UHYVE_PORT_FSYNC 		= 0x526,
 	UHYVE_PORT_FDATASYNC	= 0x527,
 	UHYVE_PORT_SYNCFS		= 0x528,
-	UHYVE_PORT_GETDENTS		= 0x529
+	UHYVE_PORT_GETDENTS		= 0x529,
+	UHYVE_PORT_DUP2			= 0X530
 } uhyve_syscall_t;
 
 typedef struct {
@@ -195,4 +196,10 @@ typedef struct {
 	int ret;
 } __attribute__((packed)) uhyve_getdeents_t;
 
+typedef struct {
+	int oldfd;
+	int newfd;
+	int ret;
+} __attribute__ ((packed)) uhyve_dup2_t;
+
 #endif // UHYVE_SYSCALLS_H

tools/uhyve.c

@@ -1339,6 +1339,14 @@ static int vcpu_loop(void)
 				break;
 			}
 
+			case UHYVE_PORT_DUP2: {
+				unsigned data = *((unsigned*)((size_t)run+run->io.data_offset));
+				uhyve_dup2_t *arg = (uhyve_dup2_t *)(guest_mem + data);
+
+				arg->ret = dup2(arg->oldfd, arg->newfd);
+				break;
+			}
+
 
 			default:
 				err(1, "KVM: unhandled KVM_EXIT_IO at port 0x%x, direction %d\n", run->io.port, run->io.direction);